<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>
		<script type="text/javascript">
			/*
			  const
			  1.必须赋初始值，赋值后不能修改
			  2.不允许重复声明
			  3.块级作用域
			  4.标识符一般大写
			  
			  定义对象类型用const
			  非对象类型用let
			*/

			var PI = 3.14; //常量
			PI = 3.1415929;

			var name = "zhangsan"; //变量

			const myPi = 3.14;
			// myPi = 3.1415926;

			// const myAge;

			const stu = {
				name: "张三",
				age: 20
			}
			
			stu.name = "王五";
			
			stu = {
				
			}

			let myName = "李四";
		</script>
	</body>
</html>
